Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnly, idempotent, and non-destructive hints. The description adds valuable behavior beyond that: it specifies the exact interval sequence (1, 3, 7, 14, 30, 60, 120, 240 days), shows a typical request/response pair, and explains that errors are returned as an 'error' object rather than a protocol error, with an example of the error message format. It also clarifies retry safety after correcting input, which is practical guidance not present in annotations.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is front-loaded with purpose, followed by a concrete example, usage guidance, and error behavior. It is longer than strictly necessary and slightly repeats annotation info (read-only/idempotent), but every section serves a distinct purpose and the structure is logical. It is not bloated and earns its length.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

The description fully covers the tool's purpose, typical input/output, usage boundaries, error handling, and safety semantics. An output schema exists, so return values are not needed, but the description gives an example anyway. There are no significant gaps for an agent to misuse this tool.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100% for both parameters, with clear descriptions for start_date and sessions, including the clamping range and default. The description's example input/output adds illustrative context but does not add new semantic detail beyond the schema. The baseline of 3 applies because the schema carries the parameter documentation burden, and the description does not materially enhance parameter understanding.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description opens with a specific verb and resource: 'Build a spaced-repetition review schedule with expanding intervals.' It clearly differentiates from the educator server's lesson_timer by stating it is not for timing a single session, which is a useful distinction even though lesson_timer is not a sibling in the provided list.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

Explicit when-to-use: 'Use when material must be reviewed on expanding intervals.' Also explicit when-not-to-use and alternative: 'Not for timing a single session, which the educator server's lesson_timer handles.' This gives the agent clear decision criteria.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.